1. Field of the Invention
The invention relates to a medical device, and more particularly, the invention relates to a medical device for delivering a non-biodegradable bulking composition to a urological site to treat urinary incontinence.
2. Brief Description of the Related Art
Urinary incontinence is an extremely common problem especially in women. In particular, many women suffer from stress incontinence. In this condition, the pelvic-floor tissues which support the urethra are weakened by, for example, childbirth or obesity. As a result, when pressure is exerted on these tissues by coughing, lifting, etc., urine is involuntarily discharged from the bladder through the urethra.
The initial treatment for stress incontinence typically consists of exercises to strengthen the pelvic-floor muscles. If these exercise are ineffective, open surgical repair of the bladder neck is often attempted. However, such surgical repair procedures are not successful for all patients. Moreover, there are always certain risks associated with open surgical procedures, such as infection, risks of anesthesia, etc.
As an alternative to surgical repair, urinary incontinence has been treated by periurethral injection therapy, in which a substance is injected into the tissue surrounding the urethra, i.e., the periurethral tissue, to add bulk to this tissue. The aim of this treatment is to restore the proximal urethra to its proper normally closed condition and to keep it closed during coughing, straining, or exercise. The injected substance compresses the urethra at the level of the bladder neck thus impeding the involuntary flow of urine from the bladder.
Many injectable substances have been tried for this purpose with varying results. For example, in the first half of the twentieth century sclerosing solutions, such as sodium morrhuate or cod liver oil were injected into the anterior vaginal wall. An inflammatory response developed with secondary scarring which resulted in compression of the incompetent urethra. Although this material was successful in curing incontinence in some patients, complications included pulmonary infarction and cardiac arrest. Similarly, paraffin and other sclerosing solutions have been tried with poor results.
More recently, polytetrafluoroethylene particles (TEFLON™, POLYTEF™) have been used as an injectable material for the correction of urinary incontinence with a success rate of from 30% to 86% in some studies. However, these particles have subsequently been demonstrated to generate foreign body granulomas and to migrate to distant organs, such as the lungs, liver, spleen and brain. Accordingly, the use of polytetrafluoroethylene particles is currently disfavored.
Another injectable material that has been used recently for the treatment of urinary incontinence is glutaraldehyde cross-linked bovine dermal collagen. However, a major problem associated with the use of collagen materials is the tendency of the implant to decrease in volume over time thereby necessitating retreatment. In addition, collagen has been associated with adverse immune responses and allergic reactions to bovine dermal collagen have been described.
Various other injectable substances have been reported or proposed as implant materials for the treatment of bladder conditions, such as vesicoureteral reflux. These substances include polyvinyl alcohol foam, glass particles, a chondrocyte-alginate suspension, and a detachable silicone balloon.
In addition to the various problems associated with many of the substances used to treat urinary incontinence, the methods currently employed for delivering injectable materials to the periurethral tissue have certain disadvantages. In particular, the amount of material necessary to compress the urethra must typically be estimated by observing the compression of the urethra wall using a cystoscope or endoscope. If an insufficient amount of material is injected in the first procedure, top-up injections administered in subsequent procedures may be necessary. In addition, the materials which are delivered may be absorbed by the body over time requiring retreatment. Other materials which are used are hydrateable and swell within the body causing difficulty in predicting a final size of the injected material.
U.S. Pat. Nos. 5,755,658 and 5,785,642, which are incorporated herein by reference in their entirety, describe methods of delivering a composition comprising a biocompatible polymer and a biocompatible solvent to the periurethral tissue. The biocompatible solvent is miscible or soluble in the fluid of the periurethral tissue and, upon contact with these fluids, the biocompatible solvent quickly diffuses away. Upon diffusion of the solvent, the biocompatible polymer precipitates to form an occlusion in the periurethral tissue which compresses the urethra thereby preventing or reducing the involuntary leakage of urine from the bladder.
However, there are certain drawbacks to the use of conventional delivery systems with the biocompatible polymer composition. In particular, the biocompatible polymer composition is injected into the periurethral tissue as a flowable composition which may not solidify instantaneously. Accordingly, it would be desirable to provide faster solidification and better control of the delivery of the biocompatible polymer composition. It would also be desirable to provide these advantages for other compositions which are delivered as two liquids to form a solid.